**1. Introduction**

Spider mites (family Tetranychidae) contains many species that are important pests of agricultural crops. According to Migeon & Dorkeld [1], who provided a database for spider mites of the world, 1300 species had been described until now. Practically all the major food crops and many ornamental plants are subject to attack [2]. Tetranychid mites feed by penetrating the plant tissue with sharp cheliceral stylets and removal of the cell contents. The chloroplasts disappear and the small amount of remaining cellular material coagulates to form an amber mass. The amount of chlorophyll in the leaves may be decreased as much as 60 percent. The mite feeding also causes inhibition of photosynthesis. Small chlorotic spots can be found at feeding sites as the mesophyll tissue collapses due to the destruction of 18–22 cells per minute. Additionally they produce silk webbing which covers the leaves. Continued feeding leads to irregular spots formed by the integration of primary suction spots; finally the leaves turn yellow, gray or bronze. In the case of sever infestation the death of plants occur [3].

A rapid rate of mite development and high reproductive abilities allow spider mites to reach harmful population levels very quickly when the conditions for growth are permissive. A great number of experimental work has been directed toward the control of these mites since they have become resistant to a number of pesticides and their control has become very difficult. Moreover, chemical

suppression of mite populations leads to residues on crops, environmental contaminations and toxicity to humans and non-target organisms. For these reasons, research has increasingly been performed to identify alternative methods to chemical control [4].
